JPH0527541A - Electrophotographic copying device - Google Patents

Abstract

PURPOSE:To provide an electrophotographic copying device which has a small number of parts, where fine color matching is possible and a photosensitive body and an intermediate transfer body are not damaged, whose life is long and whose reliability is high. CONSTITUTION:Timing for starting recording the image of each color on the photosensitive body 1 is controlled by setting an output signal that an intermediate transfer body reference detecting sensor 20 detects an intermediate transfer body reference mark 16a according to output from a time difference measuring means as reference. Consecutive printing is executed without adjusting the position of the photosensitive body 1 with respect to the intermediate transfer body 16. Therefore, the time for adjusting the position of the photosensitive body 1 with respect to the intermediate transfer body 16 is omitted, a clatch mechanism 21 is disused, production cost is drastically reduced, the fine adjustment for color matching becomes possible, and further a speed difference need not be made between the photosensitive body 1 and the intermediate transfer body 16, so that the photosensitive body 1 and the intermediate transfer body 16 are prevented from being damaged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus for forming a color image on a transfer material by superposing a plurality of monochromatic toner images.

[0002]

2. Description of the Related Art In recent years, an electrophotographic apparatus mainly uses equipment using dry toner, and has been put to practical use as a copying machine, a laser printer, etc., and has made remarkable progress. Recently, in addition to monochrome, there has been an increasing demand for colorization from the market, and a color copying machine has been released.

An electrophotographic apparatus for forming a color image by applying the electrophotographic process technology forms an image by selectively irradiating an exposure light beam corresponding to each color onto a photosensitive member having a photosensitive layer,
A plurality of electrostatic latent images respectively corresponding to specific components of a plurality of predetermined color components are developed with respective predetermined toners, and those single-color toner images are superposed to form a color on one transfer material. A method of forming an image is adopted.

For example, US Pat. No. 4,652,115
JP-A-63-292156, etc., an intermediate transfer material is provided between the photoconductor and the transfer material transporting path, and toner images of different colors individually formed on the photoconductor are occasionally printed on the intermediate transfer body. A method has been proposed in which a composite image is obtained by superimposing and transferring, and then the composite image is collectively transferred to one transfer material. However, when a single-color toner image is superposed on an intermediate transfer body, it is superposed. When the positions are displaced from each other, color unevenness occurs and the image deteriorates. Therefore, various attempts have been made to align each color.

Hereinafter, a conventional electrophotographic apparatus will be described with reference to FIGS.
This will be described with reference to FIG.

In FIG. 5, reference numeral 1 designates a photosensitive layer such as selenium (Se) or an organic photoconductor (OPC) on the outer peripheral surface of a belt base material made of a synthetic resin material or metal material in a closed loop having a joint 1a. The photoconductor is applied in a thin film form, and has a seam 1a as shown in FIGS.
Therefore, the image formation prohibited area exists near the seam 1a. The area outside this area becomes the image formation allowable area, and the transfer material 2
The image forming area is determined by the four types. As shown in FIG. 5, the photosensitive member 1 is supported in the vertical plane by two photosensitive member conveying rollers 2 and 3, and is driven by a drive motor (not shown) along the photosensitive member conveying rollers 2 and 3 along arrow A. Rotate in the direction. An arrow A is formed on the peripheral surface of the belt-shaped photoreceptor 1.
A charging device 4, an exposure optical system 5,
Developers 6B and 6B for accommodating the developer of each color of black (B), cyan (C), magenta (M), and yellow (Y).
C, 6M, 6Y, an intermediate transfer member unit 7, a photoconductor cleaning device 8, a neutralizer 9 and a photoconductor reference detection sensor 10 are provided. The charger 4 includes a charging wire 11 made of a tungsten wire or the like and a shield plate 12 made of a metal plate.
And the grid plate 13. Charge line 1
When a high voltage is applied to 1, the charging line 11 causes corona discharge to uniformly charge the photoconductor 1 via the grid plate 13. Reference numeral 14 is an exposure light beam of image data emitted from the exposure optical system 5. In the case of a laser printer, the exposure light beam 14 is controlled by a signal from a host computer (not shown) to form a plurality of electrostatic latent images on the photoconductor 1 respectively corresponding to a plurality of predetermined color components. To do. As shown in FIG. 6, the photoconductor reference detection sensor 10
Is for detecting the position of the seam 1a of the photoconductor 1,
The photoconductor reference mark 1b such as a slit arranged at the upstream end in the moving direction of the photoconductor 1 is detected at a position close to the joint of the photoconductor 1 at one end of the photoconductor 1. Each color developing device stores a toner corresponding to each color. Toner colors are selected in accordance with the respective colors, and the separating / contacting cams 15B, 15C, 15M, 15 whose both ends are rotatably supported by the machine body.
Y is rotated in response to a color selection signal from a host computer (not shown) and the selected developing device, for example, 6B is brought into contact with the photoconductor 1. The remaining unselected developing units 6C, 6M, and 6Y are separated from the photoconductor 1. The intermediate transfer body unit 7 is a seamless loop belt-shaped intermediate transfer body 16 made of a conductive synthetic resin material or the like.
And two intermediate transfer member conveying rollers 17 and 18 supporting the intermediate transfer member 16 and the intermediate transfer member 16 for transferring the toner image on the photosensitive member 1 to the intermediate transfer member 16 between them. The intermediate transfer roller 19 is disposed so as to face the body 1. Here, the outer peripheral length L1 of the photoconductor 1 is the intermediate transfer member 1
Nominally equal to the outer peripheral length L2 of 6, but L1 ≦ L2 in consideration of dimensional tolerance in mechanical fabrication and variation with time.
(That is, one cycle of the photoconductor 1 is shorter than one cycle of the intermediate transfer body 16) or L1 ≧ L2 (that is, one cycle of the photoconductor 1 is longer than one cycle of the intermediate transfer body 16). It is set to hold. Further, the photoconductor 1 and the intermediate transfer member 16 are driven by a drive source (not shown).
Are controlled by each other so that the peripheral speeds of them are the same constant speed.

Next, in FIG. 7, 20 is an intermediate transfer member 16.
The intermediate transfer body reference detection sensor detects the reference position of the intermediate transfer body, and detects the reference position by an intermediate transfer body reference mark 16a such as a slit arranged at one end of the intermediate transfer body 16. Two
Reference numeral 1 denotes a clutch mechanism provided for the photoconductor transporting rollers 2 or 3 or the intermediate transfer body transporting rollers 17 or 18, by turning on and off power from a drive source (not shown). The rotation of 16 is controlled. Reference numeral 22 denotes an intermediate transfer body cleaning device for scraping off the residual toner on the intermediate transfer body 16 after the color composite image is transferred onto the transfer material 24. Is separated from the intermediate transfer body 16 and abuts on the intermediate transfer body 16 only when it is used for cleaning. A transfer material cassette 23 stores a transfer material 24. The transfer material 24 is sent out from the transfer material cassette 23 one by one to a transfer material transport path 26 by a half-moon shaped paper feed roller 25. Reference numeral 27 denotes a registration roller for temporarily stopping and waiting the transfer material 24 in order to match the positions of the transfer material 24 and the color composite image formed on the intermediate transfer body 16, and is in pressure contact with the driven roller 28. Two
Reference numeral 9 denotes a transfer roller for transferring the color composite image formed on the intermediate transfer body 16 to the transfer material 24, and rotates in contact with the intermediate transfer body 16 only when the color composite image is transferred to the transfer material 24. 30 is a heat roller 3 having a heat source inside
1 is a fixing device including a pressure roller 32 and a transfer material 2
The color composite image transferred onto the image forming unit 4 is fixed on the thermal transfer material 24 by pressure and heat as the heat roller 31 and the pressure roller 32 are nipped and rotated to form a color image.

The operation of the electrophotographic apparatus constructed as above will be described below.

When an image forming operation command is issued, first, a high voltage is applied to the charging wire 11 in the charger 4 connected to the high voltage power source to cause corona discharge, and the surface of the photoconductor 1 is made uniform.
It is charged to about 700v to -800v. Next, photoreceptor 1
Is rotated in the direction of arrow A to irradiate the uniformly charged surface of the photosensitive member 1 with an exposure light beam 14 such as a laser beam corresponding to a predetermined black (B) image forming signal among a plurality of color components. Then, the electric charge disappears in the irradiated portion on the photoconductor 1 to form an electrostatic latent image. This electrostatic latent image is shown in Figure 1.
As shown in 0, after a predetermined image forming start time U has elapsed since the intermediate transfer member reference detection sensor 20 for detecting the reference position of the intermediate transfer member 16 detected the intermediate transfer member reference mark 16a (this time U Is constant for each color because the toner images of each color are accurately superimposed on the intermediate transfer member 16).
In addition, the seam 1a of the photoconductor 1 is formed in the image formation permitted region on the photoconductor 1 avoiding the image formation prohibited region. As shown in FIG. 10, the image forming start position is Z hours after the photoconductor reference detection sensor 10 detects the photoconductor reference mark 1b when viewed from the photoconductor side. Here, Z1 and Z2 are image formation permissible start times. That is, the photoconductor reference detection sensor 10 is the photoconductor reference mark 1
When image formation is started after a lapse of time shorter than Z1 time after detecting b, the image start position enters the image formation prohibited area, and Z2 time after the photoconductor reference detection sensor 10 detects the photoconductor reference mark 1b. When the image formation is started after a longer time has elapsed, the image end position of the image formation area enters the image formation prohibited area and image deterioration occurs. Therefore, when viewed from the side of the photoconductor 1, it is longer than Z1 time after the photoconductor reference detection sensor 10 detects the photoconductor reference mark 1b.
The intermediate transfer member is used as a reference sensor 20 within a range shorter than 2 hours.
Therefore, it is necessary to set the image forming start time after detecting the intermediate transfer member reference mark 16a.

On the other hand, the developing device 6B containing the black toner that contributes to the development is pushed in the direction of arrow D by the rotation of the separation / contact cam 15B in response to a color selection signal from a host computer (not shown), so that the photoconductor 1 is exposed. Abut. With this contact, toner adheres to the electrostatic latent image portion formed on the photoconductor 1 to form a toner image, and the development is completed. The developing device 6B which has completed the development is rotated by 180 degrees of the separation cam 15B,
It moves from the contact position with the photoconductor 1 to the separation position. The toner image formed on the photoreceptor 1 by the developing device 6B is transferred to the intermediate transfer body 16 by applying a high voltage to the intermediate transfer roller 19 arranged in contact with the photoreceptor 1 for each color. Residual toner that has not been transferred from the photoconductor 1 to the intermediate transfer member 16 is removed by the photoconductor cleaning device 8, and the charge on the photoconductor 1 from which the residual toner has been scraped off is removed by the static eliminator 9.

Next, for example, when a color of cyan (C) is selected, an image is formed on the photosensitive member 1 after the image forming start time U has elapsed after the intermediate transfer member reference mark 16a was detected by the intermediate transfer member reference detection sensor 20. Formation is started to form an electrostatic latent image on the photoconductor. Almost at the same time, the separation / contact cam 15C is rotated, and this time the developing device 6C is pushed toward the photoconductor 1,
Then, the development of cyan (C) is started. In the case of a copying machine or printer using four colors, the above-mentioned image forming operation is sequentially repeated four times, and four colors of B,
The C, M, and Y toner images are overlaid to form a color composite image.
In the color composite image thus formed on the intermediate transfer body 16, the transfer material transfer roller 29, which has been separated so far, comes into contact with the intermediate transfer body 16 and rotates, and a high pressure is applied to the transfer material transfer roller 29 and a pressure is applied. Are collectively transferred to the transfer material 24 sent from the transfer material cassette 23 along the transfer material transport path 26. Then, the transfer material 2 on which the toner image is transferred
4 is sent to the fixing device 30, where it is fixed by the heat of the heat roller 31 and the holding pressure of the pressure roller 32, and is output as a color image. The intermediate transfer body cleaning device 22 removes the residual toner on the intermediate transfer body 16 that has not been completely transferred onto the transfer material 24 by the transfer material transfer roller 29. The intermediate transfer body cleaning device 22 is separated from the intermediate transfer body 16 until one color composite image is obtained. After the color composite image is transferred to the transfer material 24 by the transfer material transfer roller 29, the intermediate transfer material cleaning device 22 comes into contact with the transfer material 24. Then, the residual toner is removed.

With the above operation, one image forming operation is completed. In this series of image forming operations, if the image formation for each color is not started after a lapse of a certain time U after the intermediate transfer member reference detection sensor 20 detects the intermediate transfer member reference mark 16a, the image shift on the intermediate transfer member 16 will occur. Occurs. However, since there is always a cycle difference between the photoconductor 1 and the intermediate transfer body 16, when the image forming operation is continued, one cycle of the photoconductor 1 is longer than one cycle of the intermediate transfer body 16 (see FIG.
0 (b)) indicates that the image forming start position on the photoconductor 1 is shorter than one cycle of the intermediate transfer member 16 (FIG. 10C). The image formation end position of (3) comes into the image formation prohibited area. Therefore, it is necessary to control the image formation start position.

The conventional image forming start position control when the period of the photosensitive member 1 is shorter than the period of the intermediate transfer member 16 will be described below.

In FIGS. 8 and 10 (a), in the first image formation, a preset image formation start time U has elapsed since the intermediate transfer member reference detection sensor 20 detected the intermediate transfer member reference mark 16a. After that (this time U is constant for each color because the toner images of the respective colors are accurately superimposed on the intermediate transfer member 16), an image avoiding the image formation prohibited area on the photosensitive member 1 where the seam 1a of the photosensitive member 1 is present. It is formed in the formation permitting region. When viewed from the side of the photoconductor 1, the image forming start position is Z time after the photoconductor reference detection sensor 10 detects the photoconductor reference mark 1b. When the image forming operation is continued, the n-th sheet has a period difference between the photoconductor 1 and the intermediate transfer member 16 as shown in FIGS. The image formation start position of the photosensitive member 1 is gradually displaced, and when viewed from the photosensitive member 1 side, the photosensitive member reference detection sensor 1
0 becomes like the ZL time after detecting the photoconductor reference mark 1a, and approaches the image forming allowable time Z2, and the image forming prohibited area is entered. Therefore, the clutch mechanism 21 provided on the drive shaft of the photoconductor conveying roller 3 of the photoconductor 1 cuts off its power for a predetermined time to decelerate or stop only the rotation of the photoconductor 1 to obtain the structure shown in FIGS. The reproduction is reproduced, and the image forming start position is adjusted again by connecting the power from the drive source by the clutch mechanism 21 and restarting the rotation.

[0015]

However, in the above structure, fine adjustment for each color shorter than the pressing time of the clutch mechanism is not possible, and the accurate adjustment corresponding to the change with time of the photosensitive member or the intermediate transfer member is not possible. It was not possible to align each color. If the image forming start position or the image forming end position of the photoconductor is likely to enter the image forming prohibited area, the image forming operation is stopped and adjustment is performed.
There has been a problem that the image forming speed becomes slower because it takes time to stop the temporary image forming operation during the image forming operation and perform the reference position alignment of the photoconductor and the intermediate transfer body.
Further, a complicated position adjusting mechanism for the photosensitive member such as a clutch and the intermediate transfer member is required, resulting in a large increase in manufacturing cost. Further, since the photoconductor and the intermediate transfer body are rotated in contact with each other due to the position adjustment, slippage occurs at the intermediate transfer section, and the slippage damages the surfaces of the photoconductor and the intermediate transfer body and pulls the image. There was also a problem of deterioration.

The present invention solves the above problems, and provides an electrophotographic apparatus having a small number of parts, capable of fine color matching, and having a long life and high reliability without damaging a photosensitive member and an intermediate transfer member. Has a purpose.

[0017]

In order to achieve the above object, the present invention is to detect a photoconductor coated with a photoconductive layer, a photoconductor reference mark provided on the photoconductor, and a photoconductor reference mark. A photosensitive member reference detection sensor that detects the reference position of the photosensitive member, a seamless loop belt-shaped or drum-shaped intermediate transfer member that serves as a medium for transferring the toner image formed on the photosensitive member to a transfer material, and intermediate transfer The intermediate transfer member reference mark provided on the body, the intermediate transfer member reference detection sensor that detects the reference position of the intermediate transfer member by detecting the intermediate transfer member reference mark, and the intermediate transfer member reference detection sensor are the intermediate transfer member reference marks. Has a time difference measuring means for measuring a time difference from the detection of the photoconductor reference detection sensor to the photoconductor reference mark, and the intermediate transfer member according to the output from the time difference measurement means. On the basis of the output signal in which the intermediate transfer member based detection sensor semi mark is detected, is obtained so as to control the timing of image recording start of each color to the photoreceptor.

[0018]

According to the present invention, the position adjustment time of the photosensitive member with respect to the intermediate transfer member is not required, the clutch mechanism can be eliminated, and the fine adjustment of the color matching can be performed and the photosensitive member and the intermediate member can be adjusted. The life of the transfer body can be extended.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An electrophotographic apparatus according to an embodiment of the present invention will be described below with reference to FIGS.

Regarding the structure and operation of each part of the electrophotographic apparatus such as charging, exposure and color development, the description of FIG. 5 is applied to the same parts as those of the conventional example shown in FIG. 5, and the same parts are given the same reference numerals. However, the description is omitted.

In the present invention, the outer peripheral length L1 of the photosensitive member 1 is nominally equal to the outer peripheral length L2 of the intermediate transfer member 16, but L1 ≦ in consideration of the dimensional tolerance in mechanical manufacturing and variation with time.
L2 (that is, one cycle (E) of the photoconductor 1 is the intermediate transfer member 1)
6 is shorter than 1 cycle (F) or L1 ≧ L2 (that is, 1 cycle (E) of the photoconductor 1 is longer than 1 cycle (F) of the intermediate transfer member 16). It is set. In addition, the photosensitive member 1 and the intermediate transfer member 16
Are each driven by a drive source (not shown), and are controlled so that their peripheral speeds become the same constant speed.

An image formation start control method for forming an image on the photoconductor 1 while avoiding the image formation prohibited area including the joint 1a of the photoconductor 1 will be described by taking the case of continuous printing as an example. Here, in the case where one cycle of the photoconductor 1 is shorter than one cycle of the intermediate transfer body 16, FIG. 1 and FIG.
Description will be given with reference to (b). Prior to image formation, the power of the device body is turned on (step 1). Then the variable n
Is set to 1 (step 1-1), the rotation of the photosensitive member 1 and the intermediate transfer member 16 is started, and the photosensitive member reference detection sensor 10 detects the intermediate transfer member reference mark 16a. The measurement of the time difference T1 until the photoconductor reference mark 1b is detected is started. This measurement is always performed while the photoconductor 1 and the intermediate transfer member 16 are rotating on a predetermined line, and this value is measured by the CPU 1 for each cycle.
02 has been updated. Then, the time difference T1 at the time of normal rotation immediately before the rotation of the initialization is finished is stored in the memory (step 2).

In the first color image forming operation,
When an image formation start operation signal is issued (step 3),
As shown in FIGS. 2 and 3, Z time (image on the photoconductor 1) after the photoconductor reference detection sensor 10 detects the time difference T1 stored in step 2 and the photoconductor reference mark 1b provided on the photoconductor 1. After the time U1 obtained by adding the elapsed time (the time during which the formation area does not cover the image formation prohibited area) is added, the exposure light beam 14 corresponding to the image formation signal of the first color of the fourth color, for example, black (B) is applied on the photoconductor 1. The initial setting image start time U1 set in the image forming start position designation register 103 so that the image is formed by irradiating the image with the image is set in the timer 101 (step 4). The initial setting image formation start time U1 is set so that the image formation start position and the image formation end position do not come to the image formation prohibited area on the photoconductor 1 described in FIG. The change in the time difference between the photoconductor 1 and the intermediate transfer member 16, that is, the cycle difference is a minute time compared to the initial setting image start time U1, and the first to the first
The lengths of the photosensitive member 1 and the intermediate transfer member 16 are set so that the image forming area of the final color of the sheet, for example, yellow (Y) does not enter the image forming prohibited area. Then, the intermediate transfer member reference detection sensor 20 detects the intermediate transfer member reference mark 16a.
Is detected and an intermediate transfer reference detection signal is output (step 5), the timer 101 is started (step 6), and an image forming signal is output after a lapse of U1 time (step 7) (step 8) and black (B) An exposure light beam 14 corresponding to an image forming signal is irradiated onto the photoconductor 1 to start image formation, and an electrostatic latent image is formed on the photoconductor 1. The electrostatic latent image formed on the photoconductor 1 is visualized by the black toner of the developing device 6B to form a toner image. The toner image formed on the photoconductor 1 is transferred onto the intermediate transfer body 16 after a lapse of Q1 after the intermediate transfer body reference detection sensor 20 detects the intermediate transfer body reference mark 16a provided on the intermediate transfer body 16. To be done.

The image formation of one color is completed (step 9),
When the image forming signal is not the signal of the final color, the process proceeds to the image formation of the next color, for example, cyan (C) as the second color (step 5). The cyan (C) toner image formed on the photoconductor 1 must be transferred onto the intermediate transfer body 16 after Q1 hours have elapsed since the intermediate transfer body reference mark 16a was detected by the intermediate transfer body reference detection sensor 20. (B) does not coincide with the start of image formation, and an image shift occurs. For that purpose, the intermediate transfer member reference mark 16a is set to the intermediate transfer member reference detection sensor 2 as in the case of forming the black (B) image.
It is sufficient to start image formation on the photoconductor 1 after a lapse of U1 time from the detection of 0. Therefore, when the next intermediate transfer member reference detection signal is output (step 5), the timer 101
Starts up (step 6) and U1 time elapses (step 7)
After that, an image forming signal is output (step 8), the exposure light beam 14 corresponding to the cyan (C) image forming signal is irradiated on the photoconductor 1 to start image formation, and an electrostatic latent image is formed on the photoconductor 1. Form. The electrostatic latent image formed on the photoconductor 1 is visualized by the cyan toner of the developing device 6C to form a toner image. Subsequently, the toner image formed on the photoconductor 1 is black on the intermediate transfer body 16 after a lapse of Q1 after the intermediate transfer body reference detection sensor 20 detects the intermediate transfer body 16a provided on the intermediate transfer body 16. It will be accurately transferred onto the toner image.

Thereafter, the same process is performed to make magenta (M)
2A and the image of yellow (Y) are formed after U1 hours have elapsed after the intermediate transfer member reference mark 16a was detected by the intermediate transfer member reference detection sensor 20, as shown in FIG. After Q1 time has elapsed since the intermediate transfer member reference detection sensor 20 detected the transfer member reference mark 16a, each color toner image is transferred onto the intermediate transfer member 16.
It is possible to obtain a color composite image without color shift. The color-superposed color composite image is transferred by the transfer material roller 29 to the transfer material 2
No. 4, and the fixing device 30 fixes it on the transfer material 24, and the first color image forming operation is completed. This is the final color. When the yellow (Y) image formation is completed, the process proceeds from step 10 to step 11. In step 11, the variable n is incremented by 1 (n = 2), and in step 12, the time difference T2 between the photosensitive member reference detection and the intermediate transfer member reference detection measured at the time of image formation of the final color is stored in the memory.
Then, if there is data for the next page in step 13, the operation proceeds to the second color image forming operation (step 4).

Next, the color image forming operation for the 21st sheet will be described with reference to FIGS. 1 and 2B. First, in step 4, Z time (the image forming area on the photoconductor 1 is not detected when the photoconductor reference detection sensor 10 detects the time difference T2 stored in the memory in step 12 and the photoconductor reference mark 1b provided on the photoconductor 1). The time U2, which is the sum of the elapsed time and the time that does not cover the image formation prohibited area), is set in the image formation start position designation register 103 and set in the timer 101. Subsequently, when the intermediate transfer member reference detection sensor 20 detects the intermediate transfer member reference mark 16a and outputs an intermediate transfer member reference signal (step 5), the timer 101 is started (step 6), and after U2 time has elapsed (step 7). An image forming signal is output (step 8), the exposure light beam 14 corresponding to the black (B) image forming signal is irradiated on the photoconductor 1 to start image formation, and an electrostatic latent image is formed on the photoconductor 1. To do. The electrostatic latent image formed on the photoconductor 1 is visualized by the black toner of the developing device 6B to form a toner image. The toner image formed on the photoconductor 1 is transferred onto the intermediate transfer body 16 after a lapse of Q2 after the intermediate transfer body reference mark 16a provided on the intermediate transfer body 16 is detected by the intermediate transfer body reference detection sensor 20. To be done.

The image formation of one color is completed (step 9),
When the image forming signal is not the signal of the final color, the process proceeds to the image formation of the next color, for example, cyan (C) as the second color (step 5). The cyan (C) toner image formed on the photoconductor 1 must be transferred onto the intermediate transfer body 16 after Q2 hours have elapsed since the intermediate transfer body reference mark 16a was detected by the intermediate transfer body reference detection sensor 20. (B) does not coincide with the start of image formation, and an image shift occurs. For that purpose, the intermediate transfer member reference mark 16a is set to the intermediate transfer member reference detection sensor 2 as in the case of forming the black (B) image.
It is sufficient to start image formation on the photoconductor 1 after a lapse of U2 time from the detection of 0. Therefore, when the next intermediate transfer member reference detection signal is output (step 5), the timer 101
Starts up (step 6) and U2 time elapses (step 7)
After that, an image forming signal is output (step 8), the exposure light beam 14 corresponding to the cyan (C) image forming signal is irradiated on the photoconductor 1 to start image formation, and an electrostatic latent image is formed on the photoconductor 1. Form. It is formed on the photoconductor 1. Then, the photoconductor 1
The toner image formed on the intermediate transfer body 16a provided on the intermediate transfer body 16 is detected by the intermediate transfer body reference detection sensor 20.
Will be accurately transferred onto the black toner image on the intermediate transfer body 16 after the lapse of Q2 after the detection.

Thereafter, the same process is performed to make magenta (M)
Image is formed on the intermediate transfer body reference mark 16a after the intermediate transfer body reference detection sensor 20 detects the intermediate transfer body reference mark 16a, and the yellow (Y) image is formed on the intermediate transfer body reference mark 16a as shown in FIG. After Q2 hours have elapsed since the intermediate transfer member reference detection sensor 20 detected the transfer member reference mark 16a, the toner image of each color is transferred onto the intermediate transfer member 16.
It is possible to obtain a color composite image without color shift. The color-superposed color composite image is collectively transferred to the transfer material 24 by the transfer material transfer roller 29, and is fixed to the transfer material 24 by the fixing device 30, and the first color image forming operation is completed. When the image formation of the final color of yellow (Y) is completed, the process proceeds from step 10 to step 11. In step 11, the variable n is incremented by 1 (n = 3), and in step 12, the time difference T3 between the photosensitive member reference detection and the intermediate transfer member reference detection measured at the time of image formation of the final color is stored in the memory. Then, if there is data for the next page in step 13, the operation proceeds to the color image forming operation for the third sheet (step 4), and the image forming operation is continued in the same manner. If there is no data for the next page, the image forming operation ends (step 14).

As described above, the intermediate transfer member reference mark 16 is formed on the photosensitive member 1 based on the time difference between the photosensitive member reference detection and the intermediate transfer member reference detection when the photosensitive member 1 and the intermediate transfer member 16 are rotated one time before.
U after a is detected by the intermediate transfer member reference detection sensor 20.
Since the image formation is started after n hours have passed, the continuous image formation operation can be continued without the image formation area entering the image formation prohibited area on the photoconductor 1.

In the above, one cycle of the photosensitive member 1 is the intermediate transfer member 1.
6 has been described as being shorter than one cycle, one cycle (E) of the photosensitive member 1 is one cycle (F) of the intermediate transfer member 16.
Even if the length is longer than that, image formation may be performed in the same flowchart as in FIG. 1 as shown in FIGS.

In the embodiment of the present invention, the initial time difference T1 is measured at the time of initialization, and the initial image forming time U1 (= T1 + Z) is set on the basis of the measured time difference T1. However, it is carried out after the color image forming start command is issued. Various methods are conceivable without departing from the gist of the present invention.

[0032]

As described above, the present invention detects the reference position of the photosensitive member by detecting the photosensitive member coated with the photosensitive layer, the photosensitive member reference mark provided on the photosensitive member, and the photosensitive member reference mark. A photosensitive member reference detection sensor, and a seamless loop belt-shaped or drum-shaped intermediate transfer member serving as a medium for transferring a toner image formed on the photosensitive member onto a transfer material,
The intermediate transfer member reference mark provided on the intermediate transfer member, the intermediate transfer member reference detection sensor that detects the reference position of the intermediate transfer member by detecting the intermediate transfer member reference mark, and the intermediate transfer member reference detection sensor It has a time difference measuring means for measuring the time difference between the reference mark detection and the photoconductor reference detection sensor detecting the photoconductor reference mark, and the intermediate transfer body reference mark is intermediately transferred according to the output from the time difference measuring means. Since the timing of starting image recording of each color on the photoconductor is controlled based on the output signal detected by the body reference detection sensor, continuous printing is possible without adjusting the position of the photoconductor with respect to the intermediate transfer body. Become. Therefore, the time for adjusting the position of the photosensitive member with respect to the intermediate transfer member can be omitted, and the clutch mechanism can be eliminated, and it is possible to greatly reduce the manufacturing cost and finely adjust the color matching. Furthermore, since it is not necessary to generate a speed difference between the photoconductor and the intermediate transfer member, damage to the photoconductor and the intermediate transfer member can be prevented, and the life of the photoconductor and the intermediate transfer member can be extended. It is possible to provide a highly reliable electrophotographic device.

[Brief description of drawings]

FIG. 1 is a flowchart of an image forming operation of an electrophotographic apparatus according to a first exemplary embodiment of the present invention.

FIG. 2 is a diagram showing an image forming state of the photoconductor and the intermediate transfer body when the cycle of the photoconductor is shorter than the cycle of the intermediate transfer body.

FIG. 3 is a diagram showing an image forming state of the photoconductor and the intermediate transfer body when the cycle of the photoconductor is longer than the cycle of the intermediate transfer body.

FIG. 4 is a block diagram of the present invention.

FIG. 5 is a partial cross-sectional view of a conventional electrophotographic apparatus and an embodiment of the present invention.

FIG. 6 is an explanatory diagram of the operation of the photosensitive member reference detection.

FIG. 7 is an operation explanatory diagram of the intermediate transfer member reference detection.

FIG. 8 is a partial cross-sectional view showing an image formation start state on the first image forming photosensitive member of the same image forming apparatus.

FIG. 9 is a partial cross-sectional view showing an image forming start state on the photoconductor after the photoconductor and the intermediate transfer body have passed a predetermined number of revolutions.

FIG. 10 is a view showing an image formation start timing on the photoconductor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 photoconductor 1a photoconductor seam 1b photoconductor reference mark 5 exposure optical system 6 developing device 10 photoconductor reference detection sensor 14 exposure light beam 16 intermediate transfer body 16a intermediate transfer body reference mark 20 intermediate transfer body reference detection sensor 24 transfer material 101 Timer 102 CPU 103 Image formation start position designation register

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location G03G 15/01 114 A 7818-2H 15/04 120 9122-2H

Claims (1)

Claim: What is claimed is: 1. A photosensitive member coated with a photosensitive layer, a photosensitive member reference mark provided on the photosensitive member, and a reference position of the photosensitive member by detecting the photosensitive member reference mark. A photoconductor reference detection sensor for detecting, a seamless loop belt-shaped or drum-shaped intermediate transfer member serving as a medium for transferring the toner image formed on the photosensitive member onto a transfer material, and the intermediate transfer member. An intermediate transfer member reference mark, an intermediate transfer member reference detection sensor that detects the reference position of the intermediate transfer member by detecting the intermediate transfer member reference mark, and the intermediate transfer member reference detection sensor is the intermediate transfer member reference mark. Has a time difference measuring means for measuring the time difference from the detection of the photoconductor reference mark by the photoconductor reference detection sensor, and the output from the time difference measurement means Accordingly, the electrophotographic apparatus is characterized in that the timing of starting image recording of each color on the photoconductor is controlled based on the output signal detected by the intermediate transfer body reference detection sensor for the intermediate transfer body reference mark. ..